1. Technical Field
The present invention relates to a deflection yoke fixed to a neck portion of a cathoderay tube. More particularly, this invention relates to an attachment structure of a magnetic piece of a deflection yoke which is fixed at a center of a coil separator in order to compensate a misconvergence in accordance with the difference of radii of curvature of a cathode ray tube screen.
2. Prior Art
Generally, a panel having a phosphor screen in a cathode-ray tube has a structure such that, in case where distance between an electron gun and a center of screen is defined as a reference radius, other radii deflected to horizontal and vertical directions are not same, and the more it goes to a peripheral portion of the screen, the more said radius of curvature increases. Because such difference of radius of curvature has been a cause of misconvergence, it has been made such that electron beam emitted from the electron gun is appropriately deflected by attaching the deflection yoke at front of the neck portion so that it reaches correctly on to the phosphor screen.
And yet, a product of saddle-toroidal type is generally used for said deflection yoke, and in the deflecting yoke of such structure, in case seeing from whole of magnetic field distribution, the horizontal deflecting coil is made in pin cushion type, while the vertical deflecting coil is made in barrel type.
In a structure of such deflecton yoke, in case when a beam emitted from the electron gun is deflected, it receives a barrel type magnetic field according to the vertical deflecting coil at a connecting portion of nect portion of the deflection yoke, and thereby a misconvergence that G beam of horizontal component of raster gets out from R and B beams in barrel type as shown in FIG. 2, and particularly a deterioration of raster of upper and lower portions of the phosphor screen is occurred very seriously, and in order to solve such disadvantage, said misconvergence is compensated by fixing a magnetic piece at a center between an opening portion and a neck portion of the coil separator.
Thus, the conventional attachment structure of the magnetic piece for compensating the misconvergence is as follows. Namely, as shown in FIG. 1, a magnetic piece 12 has been fixed to a coil separator 1 in a form that a supporting protuberance 11 having a predetermined height and length in protruded form at a central portion of the coil separator 1 is formed and a magnetic piece 12 made of concave and convex form is inserted to said supporting protuberance 11.
However, since said magnetic piece 12 is made in a structure which is supported by a supporting protuberance 11 inserted to a recess 13 formed at its central portion, in case where the deflecting coil is mounted on the coil separator 1, even if a small shock is applied to this, the magnetic piece 12 becomes to be shaken around the supporting protuberance 11, whereby a phenomenon becoming to be inclined to right and left is occurred, and according to this, the compensating magnetic field according to the magnetic piece 12 becomes to be deviated, therefore there has been occurred a problem that the electron beam becomes misconverged and distorted.
A technique has been also used heretofore in which, in order to prevent such misconvergence of electron beam, a magnetic piece is fixed to the supporting protuberance and then an adhesive tape is sticked between the magnetic piece and the coil separator so that the magnetic piece is fixed on the coil separator, however, this has produced a problem that, in case when the adhereing force of said adhesive tape would become weakened, the magnetic piece becomes to be inclined around said supporting protuberance as aforementioned, whereby it becomes to further add a bad effect according to the misconvergence.